1. Field
This disclosure relates generally to amplifiers, and more specifically, to an audio amplifier having a virtual ground.
2. Related Art
Traditional amplifiers, such as class D amplifiers used in audio applications use a system ground for coupling the amplifier to a load, such as a speaker, a headset, or an earphone. Use of the system ground requires the use of output coupling capacitors, which take up space. This poses problems for audio applications where space is limited, such as mobile devices. To address this problem, certain amplifiers use a differential output, which removes the need for a coupling capacitor. The use of differential output, however, results in two pins for coupling to the speaker, the headset, or the earphone. Moreover, stereo amplifiers need four pins for coupling to the speaker, the headset, or the earphone, when using differential output. This poses problems where there is a paucity of pins that can be used to couple to such loads. One way to reduce the number of pins in such amplifiers is to use a virtual ground. The stereo amplifiers that do use a virtual ground typically use a linear regulator to produce the virtual ground. The use of the linear regulator, however, results in lower efficiency. Moreover, in a class D audio amplifier, the linear regulator does not track changes in the supply voltage to the amplifier.
Accordingly, there is a need for an improved audio amplifier having a virtual ground.